


GREP(1)                  USER COMMANDS                    GREP(1)



NAME
     grep, egrep - print lines matching a regular expression

SYNOPSIS
     grep [ -CVbchilnsvwx ] [ -_n_u_m ] [ -AB _n_u_m ] [ [ -e ] _e_x_p_r  |
     -f _f_i_l_e ] [ _f_i_l_e_s ... ]

DESCRIPTION
     _G_r_e_p searches the files listed in the arguments (or standard
     input  if  no  files are given) for all lines that contain a
     match for the given _e_x_p_r.  If  any  lines  match,  they  are
     printed.

     Also, if any matches were  found,  _g_r_e_p  will  exit  with  a
     status  of 0, but if no matches were found it will exit with
     a status of 1.  This is useful for  building  shell  scripts
     that use _g_r_e_p as a condition for, for example, the _i_f state-
     ment.

     When invoked as _e_g_r_e_p the syntax of  the  _e_x_p_r  is  slightly
     different; See below.

REGULAR EXPRESSIONS
          (grep)    (egrep)   (explanation)

          _c         _c         a   single   (non-meta)   character
                              matches itself.

          .         .         matches any single character except
                              newline.

          \?        ?         postfix operator;  preceeding  item
                              is optional.

          *         *         postfix operator; preceeding item 0
                              or more times.

          \+        +         postfix operator; preceeding item 1
                              or more times.

          \|        |         infix  operator;   matches   either
                              argument.

          ^         ^         matches the  empty  string  at  the
                              beginning of a line.

          $         $         matches the empty string at the end
                              of a line.

          \<        \<        matches the  empty  string  at  the
                              beginning of a word.




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          \>        \>        matches the empty string at the end
                              of a word.

          [_c_h_a_r_s]   [_c_h_a_r_s]   match any character  in  the  given
                              class; if the first character after
                              [ is ^, match any character not  in
                              the given class; a range of charac-
                              ters   may    be    specified    by
                              _f_i_r_s_t-_l_a_s_t; for example, \W (below)
                              is   equivalent   to   the    class
                              [^A-Za-z0-9]

          \( \)     ( )       parentheses are  used  to  override
                              operator precedence.

          \_d_i_g_i_t    \_d_i_g_i_t    \_n matches a  repeat  of  the  text
                              matched  earlier  in  the regexp by
                              the subexpression  inside  the  nth
                              opening parenthesis.

          \         \         any special character may  be  pre-
                              ceded  by  a  backslash to match it
                              literally.

          (the following are for compatibility with GNU Emacs)

          \b        \b        matches the  empty  string  at  the
                              edge of a word.

          \B        \B        matches the empty string if not  at
                              the edge of a word.

          \w        \w        matches word-constituent characters
                              (letters & digits).

          \W        \W        matches  characters  that  are  not
                              word-constituent.

     Operator precedence is (highest to lowest) ?, *, and +, con-
     catenation, and finally |.  All other constructs are syntac-
     tically identical  to  normal  characters.   For  the  truly
     interested,  the  file  dfa.c describes (and implements) the
     exact grammar understood by the parser.

OPTIONS
     -A _n_u_m
          print <num> lines of context after every matching line

     -B _n_u_m
          print _n_u_m lines of context before every matching line

     -C   print 2 lines of context on each side of every match



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     -_n_u_m print _n_u_m lines of context on each side of every match

     -V   print the version number on the diagnostic output

     -b   print every match preceded by its byte offset

     -c   print a total count of matching lines only

     -e _e_x_p_r
          search for _e_x_p_r; useful if _e_x_p_r begins with -

     -f _f_i_l_e
          search for the expression contained in _f_i_l_e

     -h   don't display filenames on matches

     -i   ignore case difference when comparing strings

     -l   list files containing matches only

     -n   print each match preceded by its line number

     -s   run silently producing no output except error messages

     -v   print only lines that contain no matches for the <expr>

     -w   print only lines where the match is a complete word

     -x   print only lines where the match is a whole line

SEE ALSO
     emacs(1), ed(1), sh(1), _G_N_U _E_m_a_c_s _M_a_n_u_a_l

INCOMPATIBILITIES
     The following incompatibilities with UNIX _g_r_e_p exist:

          The context-dependent meaning of *  is  not  quite  the
          same (grep only).

          -b prints a byte offset instead of a block offset.

          The {_m,_n} construct of System  V  grep  is  not  imple-
          mented.

BUGS
     GNU _e?_g_r_e_p  has  been  thoroughly  debugged  and  tested  by
     several  people  over  a  period of several months; we think
     it's a reliable beast or we wouldn't distribute it.   If  by
     some  fluke  of  the  universe  you  discover  a bug, send a
     detailed description  (including  options,  regular  expres-
     sions, and a copy of an input file that can reproduce it) to
     me, mike@wheaties.ai.mit.edu.



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GREP(1)                  USER COMMANDS                    GREP(1)



     There is also a newsgroup, gnu.utils.bug, for reporting  FSF
     utility programs' bugs and fixes; but before reporting some-
     thing as a bug, please try to be sure that it  really  is  a
     bug,  not a misunderstanding or a deliberate feature.  Also,
     include the version number of the utility  program  you  are
     running in _e_v_e_r_y bug report that you send in.  Please do not
     send anything but bug reports to this newsgroup.

AVAILABILITY
     GNU _g_r_e_p is free; anyone may redistribute copies of _g_r_e_p  to
     anyone  under  the  terms  stated  in the GNU General Public
     License, a copy of which may be found in each  copy  of  _G_N_U
     _E_m_a_c_s.   See also the comment at the beginning of the source
     code file grep.c.

     Copies of GNU _g_r_e_p may sometimes be received  packaged  with
     distributions  of  Unix systems, but it is never included in
     the scope of  any  license  covering  those  systems.   Such
     inclusion  violates  the terms on which distribution is per-
     mitted.  In fact, the primary purpose of the General  Public
     License  is to prohibit anyone from attaching any other res-
     trictions to redistribution of  any  of  the  Free  Software
     Foundation programs.

AUTHORS
     Mike Haertel wrote the deterministic  regexp  code  and  the
     bulk of the program.

     James A. Woods is  responsible  for  the  hybridized  search
     strategy  of using Boyer-Moore-Gosper fixed-string search as
     a filter before calling the general regexp matcher.

     Arthur David Olson contributed code that finds fixed strings
     for  the  aforementioned  BMG  search  for  a large class of
     regexps.

     Richard Stallman wrote the backtracking regexp matcher  that
     is  used  for  \_d_i_g_i_t  backreferences, as well as the getopt
     that is provided for 4.2BSD sites.  The backtracking matcher
     was originally written for GNU Emacs.

     D. A. Gwyn wrote the C alloca emulation that is provided  so
     System  V  machines  can  run this program.  (Alloca is used
     only by RMS' backtracking matcher, and then only rarely,  so
     there  is  no  loss  if  your  machine doesn't have a "real"
     alloca.)

     Scott Anderson and Henry  Spencer  designed  the  regression
     tests used in the "regress" script.

     Paul Placeway wrote the  original  version  of  this  manual
     page.



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